Up to now, as an air conditioning apparatus applied to a vehicle making it difficult to secure a heating source for heating in a vehicle interior such as an electric vehicle, there is a type in which heating in the vehicle interior is performed with the use of a high-temperature and high-pressure refrigerant discharged from a compressor of a heat pump cycle (in other words, a vapor compression refrigeration cycle) as a heat source.
As the heat pump cycle of this type, a gas injection cycle (that is, an economizer refrigeration cycle) in which a pressure of the refrigerant is reduced in two stages between a radiator and an evaporator and a gas-phase refrigerant which is a part of an intermediate-pressure refrigerant is merged with the refrigerant of a compression process in the compressor has been known.
For example, Patent Document 1 discloses a heat pump cycle that switches from a normal cycle to a gas injection cycle during a heating operation in order to improve COP (coefficient of performance) which is a coefficient of performance of a cycle during the heating operation. In this example, the normal cycle is a one-stage compression cycle, and the gas injection cycle is a two-stage compression cycle.
More specifically, the heat pump cycle of Patent Document 1 includes first and second pressure reducing portions that reduce a pressure of a refrigerant flowing out from a radiator, a gas-liquid separator that separates gas and liquid of an intermediate-pressure refrigerant whose pressure is reduced by the first pressure reducing portion, an evaporator that evaporates the refrigerant whose pressure is reduced in the first pressure reducing portion, and the like.
In the heat pump cycle, an on-off valve for opening and closing an intermediate-pressure refrigerant passage that leads a gas-phase refrigerant separated by the gas-liquid separator to an intermediate-pressure port of the compressor is disposed in the refrigerant passage. With such a configuration, the heat pump cycle is switched between a gas injection cycle and a normal cycle other than the gas injection cycle.
In this example, when the heat pump cycle functions as the normal cycle, the second pressure reducing portion is set to a fully opened state in which a pressure reducing action is not exerted. On the other hand, when the heat pump cycle functions as the gas injection cycle, in order to reduce the pressure of the refrigerant flowing out from the radiator in two stages, both of the first and second pressure reducing portions are set to a throttling state in which the pressure reducing action is exerted.
Under the circumstances, in Patent Document 1, the on-off valve for opening and closing the intermediate-pressure refrigerant passage is configured by a differential pressure valve. The differential pressure valve opens the intermediate-pressure refrigerant passage when a differential pressure across the second pressure reducing portion becomes equal to or higher than a predetermined differential pressure. As a result, the cycle configuration of the heat pump cycle is simplified.
Further, Patent Document 2 discloses an example in which the compressor is configured by a scroll-type compressor in the heat pump cycle functioning as the gas injection cycle. More specifically, in Patent Document 2, the intermediate-pressure port is formed in an end plate portion of a fixed scroll, and the intermediate-pressure port is periodically opened and closed by a tooth tip of a movable scroll which is abutted against an end plate portion of a fixed scroll, to thereby merge the intermediate-pressure refrigerant and a refrigerant being in a compression process together.